Bart D. Ehrman, The New Testament: A Historical Introduction to the Early Christian Writings, sixth edition (OUP, 2016), 73-74.
It is important to recognize that the Pharisees were not the “power players” in Palestine in Jesus’ day. That is to say, they appear to have some popular appeal but no real political clout. In some ways they are best seen as a kind of separatist group; they wanted to maintain their own purity and did so in relative (not complete) isolate from other Jews. Many scholars think that the term “Pharisee” itself originally came from a Persian word that means “separated ones.” Eventually, however, some decades after Jesus’ execution, the Pharisees did become powerful in the political sense. This was after the Jewish War…which culminated in the destruction of Jerusalem and the Temple in the year 70 CE. With this calamity the other groups passed from the scene for a variety of reasons, and the descendants of the Pharisees were given greater authority by the Roman overlords. The oral tradition continued to grow and to be invested with greater authority. It was eventually written down around the year 200 CE and is today known as the Mishnah, the heart of the Jewish sacred collection of texts, the Talmud.